Bacillus thuringiensis Cry1A toxin-binding glycoconjugates present on the brush border membrane and in the peritrophic membrane of the Douglas-fir tussock moth are peritrophins.

Bacillus thuringiensis (Bt) Cry1A toxin-binding sites in the Douglas fir tussock moth (DFTM) larval gut were localized using immunofluorescence microscopy. Cry1Aa, Cry1Ab and Cry1Ac all bound strongly to the DFTM peritrophic membrane (PM); weaker binding of the Cry1A toxins was observed along the apical brush border of the midgut epithelium. Comparative analysis of the Cry1A toxin-binding molecules in the PM and brush border membrane vesicles (BBMVs) showed that a similar toxin-binding complex was present in both.

Localization of Bacillus thuringiensis Cry1A toxin-binding molecules in gypsy moth larval gut sections using fluorescence microscopy.

The microbial insecticide Bacillus thuringiensis (Bt) produces Cry toxins, proteins that bind to the brush border membranes of gut epithelial cells of insects that ingest it, disrupting the integrity of the membranes, and leading to cell lysis and insect death. In gypsy moth, Lymantria dispar, two toxin-binding molecules for the Cry1A class of Bt toxins have been identified: an aminopeptidase N (APN-1) and a 270kDa anionic glycoconjugate (BTR-270). Studies have shown that APN-1 has a relatively weak affinity and a very narrow specificity to Cry1Ac, the only Cry1A toxin that it binds.

Bacillus thuringiensis pore-forming toxins trigger massive shedding of GPI-anchored aminopeptidase N from gypsy moth midgut epithelial cells.

The insecticidal Cry proteins produced by Bacillus thuringiensis strains are pore-forming toxins (PFTs) that bind to the midgut brush border membrane and cause extensive damage to the midgut epithelial cells of susceptible insect larvae. Force-feeding B. thuringiensis PFTs to Lymantria dispar larvae elicited rapid and massive shedding of a glycosylphosphatidylinositol (GPI)-anchored aminopeptidase N (APN) from midgut epithelial cells into the luminal fluid, and depletion of the membrane-anchored enzyme on the midgut epithelial cells.

Identification of a Bacillus thuringiensis Cry11Ba toxin-binding aminopeptidase from the mosquito, Anopheles quadrimaculatus.

Background: Aminopeptidase N (APN) type proteins isolated from several species of lepidopteran insects have been implicated as Bacillus thuringiensis (Bt) toxin-binding proteins (receptors) for Cry toxins. We examined brush border membrane vesicle (BBMV) proteins from the mosquito Anopheles quadrimaculatus to determine if APNs from this organism would bind mosquitocidal Cry toxins that are active to it.

Results: A 100-kDa protein with APN activity (APNAnq 100) was isolated from the brush border membrane of Anopheles quadrimaculatus.

Further evidence that diapause in the gypsy moth, Lymantria dispar, is regulated by ecdysteroids: a comparison of diapause and nondiapause strains.

A nondiapause strain of the gypsy moth offers an additional tool for evaluating the regulation of diapause in this species. Patterns of protein expression in the gut and gut enzyme activity distinguished the two strains. Synthesis of a 55kDa gut protein, previously linked to diapause, began 14days after oviposition in both the diapause (D) and nondiapause (ND) strains.